JPH0571052B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention is directed to a film that is free from pinholes, cracks, local thickness unevenness, etc., and has excellent gas barrier properties during heating stretching, especially during heating high-speed stretching operations. The present invention relates to an ethylene-vinyl alcohol copolymer (hereinafter referred to as EVOH) composition with small variations in barrier properties, and is useful as a material for heat-stretched, particularly high-speed heat-stretched multilayer structures.

B. Prior Art Today, EVOH has been recognized as effective in the field of packaging films for food products, especially food products that require oxygen barrier properties, and other products that require aroma retention. There is. However, EVOH single film lacks toughness and has the drawback of not exhibiting effective barrier properties against water and water vapor.

In order to improve these drawbacks, polypropylene,
It is used in the form of a multilayer structure made by laminating a thermoplastic resin such as polystyrene and various heat sealant layers such as ionomer and ethylene vinyl acetate copolymer.

By the way, when a multilayer structure (film, sheet, balisong, etc.) manufactured by various methods is subjected to secondary processing into containers etc., especially when stretch molding is performed below the melting point of EVOH, small voids, cracks, and local deviations may occur in the EVOH layer. Meat and the like are frequently present, and as a result, the oxygen barrier properties of the molded container are greatly deteriorated. Also,
The appearance was also defective and the container could not be used as a container for food, etc.

Therefore, conventionally, EVOH generated during heating and stretching has been
For the purpose of preventing pinholes, cracks, etc. in the layer.
Addition of various plasticizers to EVOH (JP-A-53-88067,
JP-A-59-20345), blends of polyamide resins (JP-A-52-141785, JP-A-58-154755, JP-A-Sho 58-154755)
58-36412), etc., but it has been found that none of them are fully satisfactory in the following respects. In other words, in plasticizer systems such as hydroxyl group-containing systems and aromatic sulfonamide systems, the amount added must be 10 to 20 parts by weight per 100 parts by weight of EVOH in order to improve the heat-stretching properties. There are many problems such as a drastic decrease in gas barrier properties and a decrease in adhesive strength between the EVOH layer and other resin layers, which is thought to be due to plasticizer bleed, making it unusable.

On the other hand, the method of blending EVOH with polyamide resin to impart flexibility and increase secondary processability is well known, and numerous patents have been filed (Japanese Patent Laid-Open No. 44-1998).
24277, JP-A-60-24813, JP-A-58-129035, JP-A-54-38897, JP-A-58-36412, etc.), but polyamides with improved heating and high-speed stretch formability are
Perhaps due to the large chemical reaction with EVOH, there are many gel-like substances in the molded product, and the product is unusable due to significant discoloration. On the other hand, a patent has been filed for a blend system of EVOH and a polyamide resin with relatively little gel coloring, but the heat-stretching moldability at low speeds appears to be cracked, probably because the compatibility with EVOH is insufficient. Although the molded product appears to be in good condition with no pinholes or uneven thickness, the gas barrier property measurements show large variations in the measured values, suggesting the presence of minute pinholes that cannot be observed with the naked eye.
To make matters worse, as the speed of heating and stretching machines has recently increased, when heating and high-speed stretching is performed, the variation in measured values of gas barrier properties increases significantly, reducing the reliability of containers with gas barrier properties. The result is that

Therefore, it has good gas barrier properties and reliability (variation) as a barrier property container. In other words, there are minute pinholes in the EVOH layer during high-speed flammable stretching.
One of the important issues is the development of EVOH with good molding properties that do not cause cracks or uneven thickness.

C. Problems to be solved by the invention Although EVOH has various excellent properties as described above, when a laminate with thermoplastic resin is secondary processed into containers etc., cracks, pinholes, etc. may occur in the EVOH layer. Local thickness unevenness occurs, and the gas barrier properties deteriorate significantly.

Therefore, the inventors of the present invention aimed to prevent the occurrence of cracks, pinholes, local thickness unevenness, etc. in the EVOH layer that occur when secondary processing the laminate into containers, etc., without impairing the excellent gas barrier properties of EVOH. For multilayer containers with high gas barrier properties
As a result of intensive studies to develop an EVOH composition, the present invention has been completed.

D. Means for Solving the Problems The present invention consists of 100 parts by weight of EVOH with an ethylene content of 25 to 60 mol% and a saponification degree of 90% or more, and 5 to 50% of polyamide.
Polyamide (a) consisting of 30 parts by weight and containing 5 to 50% by weight of caproamide units and polyamide (b) containing 5 to 49% by weight of laurin lactam units in a ratio of a:b=5:95 to The polyamides (a) and (b) are contained in a weight ratio of 95:5.
The resin composition has a melting point of 110 to 180°C and a melt viscosity index ratio of a/b=0.1 to 10.

E Effects of the Invention Various sheets having a thermoplastic resin layer on one or both sides of the EVOH composition layer via an adhesive resin are prepared, and secondary processing and molding into cups and bottles is performed by reheating and stretching operations. At this time, it is possible to judge the moldability and gas barrier properties of the EVOH layer by measuring the appearance of the container and gas barrier properties. Therefore, the present inventors blended various plasticizers, polymers, etc. with EVOH and measured the moldability and gas barrier properties of EVOH. As a result, the melting point is 110 to 180℃, and the melting point viscosity index (melt index value measured at 190℃ and 2160g load) (MI) is 0.1 to 10g/10 minutes, especially 0.5 to 9.
The EVOH composition prepared by blending 5 to 30 parts by weight of polyamide of 100 g/10 parts by weight with respect to 100 parts by weight of EVOH appeared to be good at first glance, with fewer cracks, unevenness, uneven thickness, etc. occurring during container molding. However, when we measured the gas barrier properties (oxygen barrier properties) of the containers, we found that they were worse than the gas barrier properties of the original fabric, and even worse, there were large variations in the measured values depending on the container.
In some cases, gas barrier properties are even observed to deteriorate by 1/10 to 1/50. In particular, this tendency becomes more pronounced as the heating stretching speed increases. Therefore, this poses a serious problem to its reliability as a gas barrier container. As a result of further intensive studies, the inventors surprisingly discovered that a polyamide (a) containing 5 to 50% by weight of caproamide units and a polyamide (b) containing 5 to 49% by weight of laurin lactam units. : b = polyamide blended at a weight ratio of 5:95 to 95:5, and each polyamide has a melting point of 110 to 180°C, preferably
120~170℃, melt viscosity index ratio a/b 0.1~10
g/10 min, the polyamide is EVOH
When blended with
Not only can a very good molded product with no cracks or uneven thickness be obtained in appearance, but also
It was unexpected that a gas barrier multilayer structure with significantly improved reliability, with almost no deterioration in gas barrier properties (average value) and little variation depending on the measurement location, was obtained. Furthermore, it was found that the composition has very little gel and lumps that tend to occur during long-term extrusion molding, and that long-term stable operation performance is also greatly improved, leading to the present invention. This fact is also clear from the examples described later.

Caproamide-based polyamide has good compatibility with EVOH, but is prone to film formation abnormalities due to the formation of gels, lumps, etc. On the other hand, lauryl-lactam-based polyamide appears to have improved stretch formability with EVOH. However, during high-speed stretching, the compatibility is not necessarily good, and cracks occur at the interface between the laurinlactam polyamide and EVOH, which seems to tend to deteriorate gas barrier properties. However, as mentioned above, both polyamides are EVOH
It is truly unexpected that by blending, it exhibits excellent effects such as suppressing the generation of gels and lumps and also providing high-speed stretchability.

F. More detailed description of the invention The present invention will be explained in more detail below.

The EVOH used in the present invention is an ethylene-vinyl acetate copolymer having an ethylene content of 25 to 60%, preferably 25 to 55 mol%, and a saponification degree of the vinyl acetate component of 90% or more, preferably 95% or more. It is a combined saponified product.
When the ethylene content is less than 25 mol%, the molding temperature becomes close to the decomposition temperature, making molding difficult. On the other hand, if the ethylene content is 60 mol% or more, the gas barrier properties will be lowered and the gas barrier properties of the multilayered container will be insufficient, which is not preferable. In addition, if the degree of saponification of the vinyl acetate component is less than 95%, especially less than 90%,
With EVOH, products with little or no cracks or piholes can be obtained during container molding, but the gas barrier properties are not sufficient, so this is not preferable. Furthermore, this
EVOH is 190℃ according to ASTM-D1238-65T,
The melt viscosity index measured at 2160g load is preferable.
0.1-25g/10 minutes, more preferably 0.3-20g/
It's 10 minutes.

The caproamide units used in the present invention are 5 to 50
Polyamide containing % by weight, preferably 10-49% by weight means a copolymer of caproamide and a component copolymerizable therewith. Laurinlactam (12-
nylon), undecamide (11-nylon), hexamethylene sebacamide (6,10-nylon),
hexamethylene adipamide (66-nylon),
Amide components such as ω-aminoptanoic acid (7-nylon) and ω-aminononanoic acid (9-nylon),
Further examples include polyethers and polyesters, and particularly effective are laurin lactam (12-nylon), hexamethylene adipamide (66-nylon), and ω-aminononanoic acid (9-nylon). If the caproamide unit content is 5% by weight or less, the compatibility with EVOH will be insufficient and the measured values of gas barrier properties will vary greatly. while 50
If it exceeds % by weight, gels and lumps tend to occur frequently during multilayer sheet molding, which not only looks bad, but also increases the dispersion of gas barrier measurements during high-speed stretching. On the other hand, the polyamide containing 5 to 49% by weight, preferably 10 to 49% by weight of laurinlactam units also means a copolymer of laurinlactam and a component copolymerizable with it. Caproamide (6-
nylon), ω-aminoheptanoic acid (7-nylon), hexamethylene adipamide (66-nylon), ω-aminononanoic acid (9-nylon), undecaneamide (11-nylon), hexamethylene sebacamide (6-nylon), , 10-nylon), as well as polyethers and polyesters, among which 6-nylon, 9-nylon, 66-nylon, polyether, and polyester are particularly effective. 5% by weight of laurin lactam units
In the following, gels and unevenness tend to occur, which is unfavorable in terms of appearance, probably due to compatibility with the caproamide copolymer nylon. On the other hand, if it is 49% by weight or more,
During high-speed stretching, perhaps because the compatibility with EVOH is not sufficient,
Large variations occur in the measured values of gas barrier properties.

By the way, polyamide (a) containing 5 to 50% by weight of caproamide units and 5% by weight of laurinlactam units
The blend ratio with polyamide (b) containing ~49% by weight is a/b = 5/95 to 95/5 by weight,
Preferably a/b=20/80 to 70/30. When the content of polyamide (a) is 5% by weight or less, large variations in the measured values of gas barrier properties are observed during high-speed stretching, probably because the compatibility between the blend polyamide and EVOH is insufficient. On the other hand, if it is added in an amount of 95% by weight or more, various abnormalities are likely to occur, such as the generation of gel during film formation, the occurrence of unevenness during high-speed stretching, and variations in gas barrier property measurements. By the way, even if the above-mentioned blend polyamide is used, moldability may not necessarily be improved depending on the polyamide brand. Therefore, as a result of further study, it was found that polyamides (a) and (b) each having a melting point of 110 to 180°C and a melt viscosity index ratio of a/b = 0.1 to 10 are more preferable. The melt viscosity index of polyamide (a) and (b) is 0.1 to 10.
g/10 minutes, especially 0.5 to 9 g/10 minutes, it has been found that a multilayered container with good appearance during heating and high-speed stretching, and with less variation in gas barrier properties and gas barrier properties can be obtained.

The amount of polyamide blended is 5 to 30 parts by weight, preferably 7 to 25 parts by weight, per 100 parts by weight of EVOH. If the amount added is less than 5 parts by weight, the effect of improving moldability is not sufficient and cracks and unevenness are likely to occur. on the other hand,
If it exceeds 30 parts by weight, the gas barrier properties will be significantly reduced, making it unusable as a gas barrier container.
There are no particular limitations on the method of blending EVOH and polyamide, but there are methods such as dry blending EVOH and polyamide and drying them into pellets using a Banbury mixer single-screw or twin-screw extruder. If the blend is uneven, or if gels or lumps are generated or mixed in during the blending operation, there is a high possibility that the EVOH blend layer will break or become uneven during hot stretch molding. Using an extruder with a high degree of kneading, _N2 seal at the hopper opening,
Cold extrusion is preferred. In addition, the blended pellets were formed into a 50μ sheet using a hot press at 220℃.
When measuring the nylon particle size, the particle size is 0.1μ or less.
It is desirable that 50% or more, preferably 0.05μ or less, be 50% or more.

On the other hand, when mixing these, other additives (various resins, antioxidants, plasticizers, colorants, etc.) may be used freely within the range that does not impede the effects of the present invention. In particular, as a measure to improve the thermal stability of the resin and prevent gel formation, it is preferable to add 0.01 to 1% by weight of a hydrotalcite-based compound, hindered phenol-based, or hindered amine-based heat stabilizer.

The EVOH composition of the present invention can be prepared by the well-known melt molding method.
By compression molding, it can be molded into any molded product such as a film, sheet tube, or bottle, but as mentioned above, when this composition is used as one layer of a multilayer structure, it exhibits remarkable characteristics. This point will be explained below.

The thermoplastic resin used on at least one side of the composition layer of the present invention may be any resin that can be stretch-formed at the following temperatures, such as polypropylene resin, polystyrene resin, polyamide resin, polyvinyl chloride resin. is suitable.

When the melting point of EVOH is X℃ and the heating stretching temperature of thermoplastic resin is Y℃, X-10≧Y≧X-110 If Y is higher than (X-10)℃, during molding
Because EVOH softens and melts, it is usually possible to mold it without adding additives. On the other hand, Y is (X-
If the temperature is below 110)℃, the glass transition temperature (Tg) of the thermoplastic resin will be below room temperature, so the shape stability and dimensional changes of the molded product at room temperature will be large, making it unusable.

Methods for obtaining a multilayer structure include extrusion lamination method, dry lamination method, coextrusion lamination method, and coextrusion sheet production method (feed block or multi-manifold method) in which the EVOH composition and thermoplastic resin are bonded via an adhesive resin. A laminate is obtained by a co-extrusion pipe making method, a co-injection method, various solution coating methods, etc., and then this is processed using a vacuum-pressure deep drawing machine,
A method of reheating and stretching within a range below the melting point of EVOH using a biaxial stretching blow machine, or a method of subjecting the laminate (sheet or film) to a biaxial stretching machine and heating and stretching;
Examples include a method of co-injection and biaxial stretching of an EVOH composition and a thermoplastic resin.

Further, the thickness of the multilayer structure is not particularly limited, but when considering moldability, cost, etc., the thickness ratio of the EVOH layer to the total thickness is preferably about 2 to 20%.

Typical configurations of the multilayer structure include EVOH composition layer/adhesive resin layer/thermoplastic resin layer, thermoplastic resin layer/adhesive resin layer/EVOH composition layer/adhesive resin layer/thermoplastic resin layer. It can be cited as something. When providing thermoplastic resin layers on both outer layers, the resins may be different or the same. Here, the adhesive resin is not particularly limited as long as it can be stretch-molded at a temperature below the melting point of EVOH and can bond the EVOH composition layer and the thermoplastic resin layer, but it is preferably an ethylenic resin. Polyolefins (e.g. polyethylene, polypropylene) to which saturated carboxylic acids or their anhydrides (e.g. maleic anhydride) have been added or grafted, ethylene-vinyl acetate copolymers, ethylene-acrylic acid esters (e.g. methyl ester, ethyl ester) Examples include polymers.

In the present invention, the heat-stretched multilayer structure is a container such as a cup or bottle, or a sheet or film-like object obtained by heat-stretching as described above, and heating is a material necessary for heat-stretching the multilayer structure. Any method may be used as long as the multilayer structure is left at a certain temperature for a predetermined period of time and operated so that the multilayer structure becomes almost thermally uniform. Considering operability, it is preferable to heat the multilayer structure with various heaters to make it uniform. . The heating operation may be performed simultaneously with the stretching, or may be performed before the stretching. Stretching refers to stretching a multi-layered structure that has been heated uniformly through chucks, plugs, vacuum pressure, air, etc.
This refers to the operation of uniformly forming a container, cup, sheet, or film by blowing, etc., and either uniaxial stretching or biaxial stretching (simultaneous or sequential) can be used. In addition, the stretching ratio and stretching speed can be appropriately selected depending on the purpose, but in the present invention, high-speed stretching means
It refers to a method of uniformly forming a container or film at a high stretching speed of 5 x 10 ⁵ %/min or higher, and the molded product does not necessarily have to be oriented.

Further, in the present invention, the moisture content of the EVOH composition layer, which is a component of the multilayer structure, is not particularly limited when it is heated and stretched, but it is preferably within 0.01 to 10%.

The heated, high-speed stretched multilayer structure of the present invention thus obtained has no pinholes in the EVOH composition layer.
There are no cracks or uneven thickness, and it has extremely good gas barrier properties, with little variation in gas barrier properties, making it effective for food packaging containers and containers for cosmetics that require fragrance retention.

The present invention will be further explained below with reference to Examples.
The present invention is not limited in any way by this.

G Examples Example 1 Ethylene content 31 mol%, saponification degree 99.4%,
MI1.3g/10min EVOH (Kuraray EVAL-EP-
F101) Caproamide content 49% by weight per 100 parts by weight
6,9-nylon (mp140℃, MI=4g/10
min) (a) 7 parts by weight, and laurin lactam content 45
Weight% of 12-nylon polyether polyamide elastomer (polyoxytetramethylene content
55%, mp 160°C, MI=2g/10min) (b) (7 parts by weight) was blended and pelletized by extrusion at 200°C under N ₂ in a twin screw type vent type 40φ extruder. The obtained pellets were dried at 80°C for 8 hours.
Use this pellet to make feedblock molds of 3 types and 5 types.
A sheet was prepared by applying it to a layer coextrusion device. The sheet is composed of both outermost layers of polypropylene (Mitsubishi Noblen MA-6) of 800 μm or adhesive resin layers (Mitsubishi Yuka Models P-300F maleic anhydride modified polypropylene) of 50 μm each, and the innermost layer (center) is the above EVOH layer. It is 50μ. The obtained sheet was applied to a vacuum-pressure forming machine (stretching speed 9 x 10 ⁵ %/min),
Thermoforming (SPPF molding) was performed at ℃. The obtained molded product had good transparency and appearance, and had no cracks or uneven thickness. 20℃・65%RH of this container
When gas barrier properties ^were measured at
Not only does it exhibit very good gas barrier properties compared to atm, but the variation in oxygen permeability measurements (R - maximum value - minimum value) when measuring 10 samples is 0.1 cc.
It was a very small and good barrier container of 20 μ/m ² / 24 hr / atm.

Example 2 In Example 1, both outermost layers were changed from polypropylene to polystyrene (Idemitsu styrene ET-61),
In addition, the same procedure as in Example 1 was carried out except that the adhesive resin layer was changed from MODETSUKU P・300F to MERSEN M-5420 (maleic anhydride-modified ethylene-vinyl acetate resin manufactured by Toyo Soda). The test was carried out at a speed of 9×10 ⁵ %/min). The appearance of the obtained molded product was good, with no cracks or uneven thickness. When we measured the gas barrier properties of this container, we found that the oxygen permeability was 0.6cc・20μ/ ^m2・24hr・atm(20
℃・65%RH), and the variation (R) in barrier properties of 10 samples is 0.2cc・20μ/m ²・24hr・atm
It was a small and good barrier container.

Comparative Example 1 In Example 2, the amount of polyamide blend {(a) and
Total amount of (b)} 14 parts by weight {2 parts by weight of (a) + 4 parts by weight
(b) 2 parts by weight}, and the same procedure as in Example 2 was carried out. As a result, there are many cracks and uneven thickness, and the gas barrier properties are reduced to an oxygen permeability of 5c.c.・20μ/m ²・
It was too long to withstand use at 24hr/ATM.

Comparative Example 2 In Example 2, only 14 parts by weight of 12-nylon polyether polyamide elastomer (b) with a laurin lactam content of 45% by weight was added as the polyamide (6,9-nylon (a) was 0). A test was conducted in the same manner as in Example 2. As a result, the multilayer sheet was in good condition, and no cracks, uneven thickness, etc. were visually observed in the container that had been heated and stretched at high speed. However, when gas barrier properties were measured, not only was the oxygen permeability 0.95cc/20μ/ ^m2 /24hr/atm, which was high, but the variation (R) of the gas barrier measurements measured on 20 samples was 4.1cc/m2/24hr/atm. 20μ/ ^m2・24hr・
ATM, which is high, made it impossible to put it to practical use due to its reliability as a gas barrier container.

Comparative Example 3 In Comparative Example 2, the molding speed of the vacuum-pressure forming machine was significantly lowered and the stretching speed was set to 10 ⁵ %/min.
Thickness unevenness) tends to be slightly improved compared to Comparative Example 2, and the gas barrier properties of the container (average value) are slightly improved with an oxygen permeability of 0.7cc・20μ/m ²・24hr・atm, and the measured values The variation is 0.9cc・20μ/ ^m2・
There was a tendency to decrease to 24hr/atm. This shows that variations in moldability and gas barrier properties largely depend on the molding speed (stretching speed). In other words, it is clear from this comparative example how important and highly desired the quality stability and reliability of molded products are in recent years due to increased molding speeds.

Example 3 In Example 2, EVOH has an ethylene content of 44
mol%, saponification degree 99.5%, MI 5.4g/10 min (EVAL-EP E105 manufactured by Kuraray), and as polyamide, 6,12 with a caproamide content of 30% by weight.
- 6,12 of 5 parts by weight of nylon (mp160°C, MI=4g/10min) and 30% by weight of laurinlactam content
- The same procedure as in Example 2 was carried out except that the amount was changed to 10 parts by weight of nylon (mp175°C, MI=4g/10min). As a result, the appearance of the obtained molded product was good, and there were no cracks or uneven thickness. The gas barrier properties of this container are: oxygen permeability 1.5cc・20μ/m ²・24hr・atm
(20℃－65%RH), and the variation (R) of asbarrier measurement values among 20 samples is 0.2cc・20μ/
It was a small container with a good gas barrier of ^m2 , 24 hours, and ATM.

Comparative Example 4 In Example 3, 15 parts by weight of polyamide {(a) and
caproamide content of 57% by weight instead of (total amount of (b))
6,12-nylon (mp150℃, MI=4g/10
Example 3 was carried out in the same manner as in Example 3, except that 15 parts by weight was used. As a result, the generation of bumps and gels was observed during the production of the multilayer sheet, and uneven spread in the bumps and gel portions and tearing of the EVOH blend layer were observed during high-speed stretching. Furthermore, when gas barrier properties were measured, oxygen permeability was 2.3cc・20μ/ ^m2・24hr・
atm, and the variation (R) of gas barrier measurement values among 20 samples is 4.8cc・20μ/ ^m2・
It was too large to be used at 24hr/ATM.

Comparative Example 5 In Example 2, the amount of polyamide blend {(a) and
Total amount of (b)} 14 parts by weight 40 parts by weight {(a) 20 parts by weight +
(b) 20 parts by weight}, and the rest was carried out in the same manner as in Example 2. As a result, the gas barrier property of the container was 4.5
cc, 20μ/ ^m2 , 24hr, ATM, it was too large to withstand use.

Comparative Example 6 In Example 3, 6,12-nylon (m.
p.160°C, MI=4g/10min) The same procedure as in Example 3 was carried out except that 15 parts by weight of (a) alone was used. As a result, it was observed that spots and gels were generated during the production of the multilayer sheet. Furthermore, when gas barrier properties were measured, the oxygen permeability was as high as 2.2 cc/20 μ/m ^2/24 hr/atm, and the variation (R) in gas barrier properties among 20 ampoules was 4.2 cc/20 μ/m 2/24 ^hr .・Big as ATM,
It was unusable.

Claims (1)

[Claims] 1. Ethylene content 25 to 60 mol%, silicification degree 90%
More than 100 ethylene-vinyl alcohol copolymers
parts by weight and 5 to 30 parts by weight of polyamide,
and the polyamide consists of a polyamide (a) containing 5 to 50% by weight of caproamide units and a polyamide (b) containing 5 to 49% by weight of laurin lactam units, and the weight of the polyamides (a) and (b) The ratio of a:b is 5:95 to 95:5, and the melting points of polyamides (a) and (b) are 110 to 180°C, and the ratio of melt viscosity index is a/b.
A resin composition in which b=0.1 to 10. 2. The resin composition according to claim 1, wherein each of (a) and (b) has a melting point of 120 to 170°C. 3 Melt viscosity index of polyamide is 0.5-9g/10
The resin composition according to claim 1, which is